The first goal of the proposed project is to develop statistical techniques to analyze non-random data on ambient air levels of workplace hazards in the OSHA Management Information System (MIS). The second goal is to evaluate the impact of OSHA health policies on occupational air concentrations for two major workplace hazards regulated by the agency, using the OSHA inspection data. I have on data tapes the complete records from the OSHA MIS of all OSHA inspections carried out from 1972 through 1982. Analysis of the data to make cross-plant comparisons presents substantial statistical problems because the orientation toward documenting violations leads to non-random inspection, sampling, and reporting processes. The opportunities for bias with the non-random processes are substantial, due to the relatively low coverage rates for each of the processes. The project will produce two products. The first paper will formally treat a range of statistical issues that arise in pooling industrial hygiene data across plants, based on work performed in conjuction with industrial hygiene inspectors. This paper will provide a useful framework for subsequent use of the data for studies of the impact of OSHA regulatory standards and enforcement policies on workplace air levels of hazards. The analysis will consider various recommendations for changing the reporting requirements for the OSHA MIS to make the data more useful for such studies. A second product will be a longitudinal study of two hazardous substances regulated by OSHA, including a re-analysis of the asbestos data in the principal investigator's dissertation. As with the earlier asbestos study, the focus will be on analyzing the determinants of agency decisions regarding enforcement policy (where to inspect, how much to fine when violations are detected) and company behavior regarding the control of exposures. By employing the Heckman techniques for correcting sample selection bias, it will be possible to project exposure performance for the universe of firms (with potential exposures) on the basis of the performance of inspected firms. Substances under consideration include silica, lead, coke oven emissions, noise, vinyl chloride, and carbon monoxide. Others may also be considered.